The proposed research will investigate non-human primate vocal communication and it's possible biological and evolutionary relationships to human language. Laboratory studies will be conducted on how baboons recognize differences their own highly vowel-like "grunt" vocalizations, and the results contrasted with how humans perceive the same baboon vocalizations. The studies will focus on the perception of both natural and synthetic variants of the affiliative "grunt" calls of baboons, and will complement prior work on both vocal analyses and field studies of these same baboon grunt calls. One set of experiments will determine how baboons use the acoustic features of vowel-like grunt calls to recognize a vocalizer's sex, and to test for the relative importance of specific acoustic cues that are likely to be important in these discriminations. Experiments will examine, in both baboons and humans, the generalization of male/female grunt calls to new tokens, use synthetic grunts to test the relative importance of fundamental frequency (F0) and formant patterning in these discriminations, and measure discrimination thresholds for recognition of vocalizer sex. A second set of experiments will determine how baboons use the acoustic features of vowel-like grunt calls to recognize other individuals, and also test for the relative importance of specific acoustic cues (F0, formant spacing) that are likely to be important in these discriminations. A third set of experiments will determine how baboons categorize vowel-like grunts based on their functional significance (i.e., "move" versus "infant" grunts) in the face of acoustic variation related to the sex and individual identity of the vocalizer. Experiments will characterize discrimination and labeling functions for natural and synthetic "move" and "infant" grunts in both baboons and humans (as a control group) to determine whether these grunt types are perceived in a linguistic-like fashion. The proposed research will extend our knowledge of the acoustic communication abilities of baboons and their relationships to the evolution of human communication.